HUMAN DIGESTIVE SYSTEM PDF IN HINDI
To do this, the digestive system is specialized to ingest food, propel it through the This chapter presents the general anatomy of the digestive system (), followed by with essentially everything humans put into their mouths. Some. called digestion and is carried out by our digestive system by mechanical The human digestive system consists of the alimentary canal and the associated. 6 सितंबर Biology Gk: Human Body | पाचन तंत्र |Digestive System the body absorb- able, This chemical process of organisms is called digestive system. . RRB NTPC Syllabus Railway NTPC Syllabus in Hindi | PDF.
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Human Digestive System PDF for, SSC CGL, CPO SSC CHSL, RRB Exams, UPSC and other public Solar System in Hindi | सौरमंडल. What is the function of the digestive system? Read about the human digestive system and its functions and organs. The mouth, stomach, intestines, gallbladder, . The human digestive system consists of the gastrointestinal tract plus the accessory organs of Create a book · Download as PDF · Printable version.
The sphincter also serves to prevent back flow from the esophagus into the pharynx. The esophagus has a mucous membrane and the epithelium which has a protective function is continuously replaced due to the volume of food that passes inside the esophagus. During swallowing, food passes from the mouth through the pharynx into the esophagus. The epiglottis folds down to a more horizontal position to direct the food into the esophagus, and away from the trachea.
Once in the esophagus, the bolus travels down to the stomach via rhythmic contraction and relaxation of muscles known as peristalsis. The lower esophageal sphincter is a muscular sphincter surrounding the lower part of the esophagus.
Human digestive system
The junction between the esophagus and the stomach the gastroesophageal junction is controlled by the lower esophageal sphincter, which remains constricted at all times other than during swallowing and vomiting to prevent the contents of the stomach from entering the esophagus. As the esophagus does not have the same protection from acid as the stomach, any failure of this sphincter can lead to heartburn.
The esophagus has a mucous membrane of epithelium which has a protective function as well as providing a smooth surface for the passage of food. Due to the high volume of food that is passed over time, this membrane is continuously renewed.
Adult digestive system Diaphragm The diaphragm is an important part of the body's digestive system. The muscular diaphragm separates the thoracic cavity from the abdominal cavity where most of the digestive organs are located. The suspensory muscle attaches the ascending duodenum to the diaphragm. This muscle is thought to be of help in the digestive system in that its attachment offers a wider angle to the duodenojejunal flexure for the easier passage of digesting material.
The diaphragm also attaches to, and anchors the liver at its bare area. The esophagus enters the abdomen through a hole in the diaphragm at the level of T Stomach Main article: Stomach Areas of the stomach The stomach is a major organ of the gastrointestinal tract and digestive system.
It is a consistently J-shaped organ joined to the esophagus at its upper end and to the duodenum at its lower end.
Human Digestive System | Digestive Glands
Gastric acid informally gastric juice , produced in the stomach plays a vital role in the digestive process, and mainly contains hydrochloric acid and sodium chloride.
A peptide hormone , gastrin , produced by G cells in the gastric glands , stimulates the production of gastric juice which activates the digestive enzymes.
Pepsinogen is a precursor enzyme zymogen produced by the gastric chief cells , and gastric acid activates this to the enzyme pepsin which begins the digestion of proteins. As these two chemicals would damage the stomach wall, mucus is secreted by innumerable gastric glands in the stomach, to provide a slimy protective layer against the damaging effects of the chemicals on the inner layers of the stomach.
At the same time that protein is being digested, mechanical churning occurs through the action of peristalsis , waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Gastric lipase secreted by the chief cells in the fundic glands in the gastric mucosa of the stomach, is an acidic lipase, in contrast with the alkaline pancreatic lipase.
This breaks down fats to some degree though is not as efficient as the pancreatic lipase.
The pylorus , the lowest section of the stomach which attaches to the duodenum via the pyloric canal , contains countless glands which secrete digestive enzymes including gastrin. After an hour or two, a thick semi-liquid called chyme is produced. When the pyloric sphincter , or valve opens, chyme enters the duodenum where it mixes further with digestive enzymes from the pancreas, and then passes through the small intestine, where digestion continues.
When the chyme is fully digested, it is absorbed into the blood. Water and minerals are reabsorbed back into the blood in the colon of the large intestine, where the environment is slightly acidic. Some vitamins, such as biotin and vitamin K produced by bacteria in the gut flora of the colon are also absorbed.
The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B Vitamin B12 cobalamin , is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands - transcobalamin I also called haptocorrin , which protects the acid-sensitive vitamin from the acidic stomach contents.
Once in the more neutral duodenum, pancreatic enzymes break down the protective glycoprotein. The freed vitamin B12 then binds to intrinsic factor which is then absorbed by the enterocytes in the ileum.
The stomach is a distensible organ and can normally expand to hold about one litre of food. The stomach of a newborn baby will only be able to expand to retain about 30 ml.
Spleen Main article: Spleen The spleen breaks down both red and white blood cells that are spent. This is why it is sometimes known as the 'graveyard of red blood cells'.
A product of this digestion is the pigment bilirubin , which is sent to the liver and secreted in the bile. Another product is iron , which is used in the formation of new blood cells in the bone marrow.
The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites ; synthesise proteins and produce biochemicals needed for digestion. It regulates the storage of glycogen which it can form from glucose glycogenesis.
The liver can also synthesise glucose from certain amino acids.
Its digestive functions are largely involved with the breaking down of carbohydrates. It also maintains protein metabolism in its synthesis and degradation. In lipid metabolism it synthesises cholesterol. Fats are also produced in the process of lipogenesis.
The liver synthesises the bulk of lipoproteins. The liver is located in the upper right quadrant of the abdomen and below the diaphragm to which it is attached at one part, This is to the right of the stomach and it overlies the gall bladder. The liver produces bile , an important alkaline compound which aids digestion.
Bile acts partly as a surfactant which lowers the surface tension between either two liquids or a solid and a liquid and helps to emulsify the fats in the chyme. Food fat is dispersed by the action of bile into smaller units called micelles. The breaking down into micelles creates a much larger surface area for the pancreatic enzyme, lipase to work on.
Lipase digests the triglycerides which are broken down into two fatty acids and a monoglyceride. These are then absorbed by villi on the intestinal wall. If fats are not absorbed in this way in the small intestine problems can arise later in the large intestine which is not equipped to absorb fats.
Bile also helps in the absorption of vitamin K from the diet. Bile is collected and delivered through the common hepatic duct. This duct joins with the cystic duct to connect in a common bile duct with the gallbladder. Bile is stored in the gallbladder for release when food is discharged into the duodenum and also after a few hours.
Bile flows from the liver through the bile ducts and into the gall bladder for storage. The bile is released in response to cholecystokinin CCK a peptide hormone released from the duodenum. The production of CCK by endocrine cells of the duodenum is stimulated by the presence of fat in the duodenum.
The neck tapers and connects to the biliary tract via the cystic duct , which then joins the common hepatic duct to form the common bile duct. At this junction is a mucosal fold called Hartmann's pouch, where gallstones commonly get stuck. The muscular layer of the body is of smooth muscle tissue that helps the gallbladder contract, so that it can discharge its bile into the bile duct.
The gallbladder needs to store bile in a natural, semi-liquid form at all times. Hydrogen ions secreted from the inner lining of the gallbladder keep the bile acidic enough to prevent hardening. To dilute the bile, water and electrolytes from the digestion system are added. Also, salts attach themselves to cholesterol molecules in the bile to keep them from crystallising.
If there is too much cholesterol or bilirubin in the bile, or if the gallbladder doesn't empty properly the systems can fail. This is how gallstones form when a small piece of calcium gets coated with either cholesterol or bilirubin and the bile crystallises and forms a gallstone. The main purpose of the gallbladder is to store and release bile, or gall. Bile is released into the small intestine in order to help in the digestion of fats by breaking down larger molecules into smaller ones.
After the fat is absorbed, the bile is also absorbed and transported back to the liver for reuse. Pancreas Action of digestive hormones Pancreas, duodenum and bile duct The pancreas is a major organ functioning as an accessory digestive gland in the digestive system. It is both an endocrine gland and an exocrine gland.
The endocrine part releases glucagon when the blood sugar is low; glucagon allows stored sugar to be broken down into glucose by the liver in order to re-balance the sugar levels.
The pancreas produces and releases important digestive enzymes in the pancreatic juice that it delivers to the duodenum. The pancreas lies below and at the back of the stomach. It connects to the duodenum via the pancreatic duct which it joins near to the bile duct's connection where both the bile and pancreatic juice can act on the chyme that is released from the stomach into the duodenum. Aqueous pancreatic secretions from pancreatic duct cells contain bicarbonate ions which are alkaline and help with the bile to neutralise the acidic chyme that is churned out by the stomach.
The pancreas is also the main source of enzymes for the digestion of fats and proteins. Some of these are released in response to the production of CKK in the duodenum. The enzymes that digest polysaccharides, by contrast, are primarily produced by the walls of the intestines. The cells are filled with secretory granules containing the precursor digestive enzymes.
The major proteases , the pancreatic enzymes which work on proteins, are trypsinogen and chymotrypsinogen. Elastase is also produced. Smaller amounts of lipase and amylase are secreted. The pancreas also secretes phospholipase A2 , lysophospholipase , and cholesterol esterase.
The precursor zymogens , are inactive variants of the enzymes; which avoids the onset of pancreatitis caused by autodegradation. Once released in the intestine, the enzyme enteropeptidase present in the intestinal mucosa activates trypsinogen by cleaving it to form trypsin; further cleavage results in chymotripsin. Lower gastrointestinal tract Main article: Gastrointestinal tract The lower gastrointestinal tract GI , includes the small intestine and all of the large intestine.
The lower GI starts at the pyloric sphincter of the stomach and finishes at the anus. The small intestine is subdivided into the duodenum , the jejunum and the ileum. The cecum marks the division between the small and large intestine.
The large intestine includes the rectum and anal canal. After two hours the stomach has emptied. In the small intestine, the pH becomes crucial; it needs to be finely balanced in order to activate digestive enzymes.
The chyme is very acidic, with a low pH, having been released from the stomach and needs to be made much more alkaline. This is achieved in the duodenum by the addition of bile from the gall bladder combined with the bicarbonate secretions from the pancreatic duct and also from secretions of bicarbonate-rich mucus from duodenal glands known as Brunner's glands. The chyme arrives in the intestines having been released from the stomach through the opening of the pyloric sphincter. The resulting alkaline fluid mix neutralises the gastric acid which would damage the lining of the intestine.
The mucus component lubricates the walls of the intestine.
(Hindi) Biology Class 11 - Digestion and Absorption
When the digested food particles are reduced enough in size and composition, they can be absorbed by the intestinal wall and carried to the bloodstream. The first receptacle for this chyme is the duodenal bulb. From here it passes into the first of the three sections of the small intestine, the duodenum. The next section is the jejunum and the third is the ileum. The duodenum is the first and shortest section of the small intestine. It is a hollow, jointed C-shaped tube connecting the stomach to the jejunum.
It starts at the duodenal bulb and ends at the suspensory muscle of duodenum. The attachment of the suspensory muscle to the diaphragm is thought to help the passage of food by making a wider angle at its attachment.
Most food digestion takes place in the small intestine. Segmentation contractions act to mix and move the chyme more slowly in the small intestine allowing more time for absorption and these continue in the large intestine. In the duodenum, pancreatic lipase is secreted together with a co-enzyme , colipase to further digest the fat content of the chyme.
From this breakdown, smaller particles of emulsified fats called chylomicrons are produced. There are also digestive cells called enterocytes lining the intestines the majority being in the small intestine. They are unusual cells in that they have villi on their surface which in turn have innumerable microvilli on their surface. All these villi make for a greater surface area, not only for the absorption of chyme but also for its further digestion by large numbers of digestive enzymes present on the microvilli.
The chylomicrons are small enough to pass through the enterocyte villi and into their lymph capillaries called lacteals. A milky fluid called chyle , consisting mainly of the emulsified fats of the chylomicrons, results from the absorbed mix with the lymph in the lacteals.
The suspensory muscle marks the end of the duodenum and the division between the upper gastrointestinal tract and the lower GI tract. The digestive tract continues as the jejunum which continues as the ileum. The jejunum, the midsection of the small intestine contains circular folds , flaps of doubled mucosal membrane which partially encircle and sometimes completely encircle the lumen of the intestine.
These folds together with villi serve to increase the surface area of the jejunum enabling an increased absorption of digested sugars, amino acids and fatty acids into the bloodstream. The circular folds also slow the passage of food giving more time for nutrients to be absorbed. The last part of the small intestine is the ileum. This also contains villi and vitamin B12 ; bile acids and any residue nutrients are absorbed here. When the chyme is exhausted of its nutrients the remaining waste material changes into the semi-solids called feces , which pass to the large intestine, where bacteria in the gut flora further break down residual proteins and starches.
At this junction there is a sphincter or valve, the ileocecal valve which slows the passage of chyme from the ileum, allowing further digestion. It is also the site of the appendix attachment. Large intestine In the large intestine ,  the passage of the digesting food in the colon is a lot slower, taking from 12 to 50 hours until it is removed by defecation.
The colon mainly serves as a site for the fermentation of digestible matter by the gut flora. The time taken varies considerably between individuals. The remaining semi-solid waste is termed feces and is removed by the coordinated contractions of the intestinal walls, termed peristalsis , which propels the excreta forward to reach the rectum and exit via defecation from the anus.
The wall has an outer layer of longitudinal muscles, the taeniae coli , and an inner layer of circular muscles. Protein digestion occurs in the stomach.
Here pancreatic juice comes from pancreatic, it contains three types of enzymes — Trypsin — converts proteins and peptones into polypeptides and amino acids.
Amylase — converts the starch into a solution of dissolved sugar. Lipase -emulsified converts fats into glycerin and fatty acids. After the duodenum, the food goes into the small intestine, which is approximately 22 feet long tube. It is also called ileium. The glands are found on the walls of the small intestine, which provides various types of enzymes.
Large molecules of food with these juices become absorbable by splitting in small molecules. After the small intestine, the remaining absorption of food comes in the large intestine, where water is absorbed. After this action the residual substance goes into the rectum as the stool and goes out of the body by the anus. The large intestine has no specific role in digestive function, its main function is to absorb water from food. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.
British Governor Generals and Viceroys in India. Latest Current Affairs Site Geography of India Biology Gk: Latest Brand Ambassador Quiz: Alloy and Components Quiz: Animals and their species or breed Quiz:See also gastrointestinal tract. The bile duct and the pancreatic duct open together into the duodenum as the common hepato-pancreatic duct which is guarded by a sphincter called the sphincter of Oddi.
Non-destructive digestion Some nutrients are complex molecules for example vitamin B12 which would be destroyed if they were broken down into their functional groups. Most parts of the GI tract are covered with serous membranes and have a mesentery.
Digestion is separated into four steps: Ingestion : placing food into the mouth entry of food in the digestive system , Mechanical and chemical breakdown: mastication and the mixing of the resulting bolus with water, acids , bile and enzymes in the stomach and intestine to break down complex molecules into simple structures, Absorption: of nutrients from the digestive system to the circulatory and lymphatic capillaries through osmosis , active transport , and diffusion , and Egestion Excretion : Removal of undigested materials from the digestive tract through defecation.
Pancreas Action of digestive hormones Pancreas, duodenum and bile duct The pancreas is a major organ functioning as an accessory digestive gland in the digestive system. Which makes the path of digestion easier. Esophagus Main article: Esophagus The esophagus , commonly known as the foodpipe or gullet, consists of a muscular tube through which food passes from the pharynx to the stomach.
Also, salts attach themselves to cholesterol molecules in the bile to keep them from crystallising.
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